Chlorinated hydrocarbons have been widely introduced into the environment as a by-product of agriculture and are known to be toxic to mice and humans in high doses. Exactly how they affect wildlife at the concentrations present in the environment, however, is not well characterized, although animals in lakes and waterways that are polluted by these types of compounds appear to suffer greatly. The broad goal of this project is to advance our understanding of why this is so. More narrowly, we propose to study how these compounds affect the endocrine systems of 3 species of wildlife, alligators, large-mouth bass and brown bullhead catfish within a highly polluted lake in Central Florida, lake Apopka. This lake is adjacent to a Superfund site, the Tower Chemical Co. site, which is polluted with dicofol from a major spill in 1980. The spill included 15% DDT and its metabolites DDD, DDE and chloro-DDT. Muck farming, citrus, widely used pesticides and a sewage treatment facility have also added to the pollution in this lake. We have chosen to study species that may be demonstrating different sensitivities to contaminants. Initialy observations indicate that the lake's alligator and large-mouth bass populations are at risk, while brown bullhead catfish appear to be thriving. We propose to study these species both in the field and laboratory as summarized within three specific aims: 1: survey and identify potential xenobiotic contaminants in central Florida's Lake Apopka relative to cleaner control lakes in the same region, that may affect reproductive and endocrine function in alligators and fish, 2: treat alligators and fish, in captivity, as well as eggs and embryos, with chlorinated hydrocarbons or combinations of previously identified xenobiotic compounds to determine their direct and multigenerational effects on reproductive and endocrine function, 3: identify and characterize specific bioindicators and biomarkers for the development of in-vitro test systems and diagnostic procedures for the evaluation of the biochemical effects of specified chlorinated hydrocarbon contaminants. Because wildlife often act as sentinels of contaminant exposure for humans, the results we generate in this work may have value in understanding better how chlorinated hydrocarbons harm human health.